For 2-3 degrees, a proper snow jacket with down filling and snow pants is more than enough. Infact, you can make him wear a normal jacket as well (water proof) in that weather. T-shirt and pants inside. Gloves (snow gloves) and beanie (wool cap), one pair of socks and snow boots if he wants to walk or play in the snow. Snow boots only when there is snow on the ground, not otherwise
From -5 Upto -15 my son wears a full sleeve Tshirt, fleece jacket and down jacket on top and pants and snow pants at the bottom.
For -16 to -25, a full sleeve Tshirt, a sweater, a hoodie and snow jacket on top. Bottom fleece pants (fleece on the inside) and jeans and snow pants.
Below -25 it's a thermal top, woolen Tshirt or fleece shirt (fleece inside), hoodie and snow jacket with thermal bottoms, jeans or fleece tracks and snow pants at the bottom. In this weather he'd be wearing 2 pairs of socks. A normal pair of socks inside and the regular feet warmers over those
Beanie and gloves remain standard for all weather. For below -25 he woolen gloves under the normal gloves.
